Electrodeposition of nickel



United States Patent 3,264,200 ELECTRODEPOSITION 0F NICKEL Richard J.Clauss, Allen Park, and Henry Brown, Huntington Woods, Mich., assignorsto The Udylite Corporation, Warren, Mich, a corporation of Delaware NoDrawing. Filed Jan. 16, 1964, Ser. No. 338,026 8 Claims. (Cl. 204-49)This invention relates to the electrodeposition of nickel and inparticular to the plating of ductile semi-bright nickel from aqueousacidic nickel electroplating solutions.

It is well-known in the art that certain aryl sulfonic acids andsulfonamides such as benzene sulfonic acid, naphthalene sulfonic acid,and benzene sulfonamide cause brightening in the nickel deposit obtainedfrom acidic nickel solutions. These aryl sulfon compounds are generallyused in conjunction with other types of addition agents such as activeunsaturated compounds to obtain fully brilliant bright nickel deposits.

The essential feature which has characterized all of the previous arylsulfon compounds used in nickel electroplating solutions, whether usedalone or in combinations, has been the introduction of appreciableamounts of sulfur into the nickel deposit as nickel sulfide.

This invention is based upon the discovery that one particular arylsulfon compound, metasulfobenzoic acid,

COOH

may be added to aqueous, acidic nickel solutions in appreciableconcentration without introducing more than a very slight trace ofsulfur into the nickel deposit. With the use of this compound, theconcentration of sulfur in the nickel deposit usually is about 0.005%which is of the order of to A the concentration which arises from theuse, in similar concentrations, of other aryl sulfon type compounds suchas benzene mono-, and di-sulfonic acids, benzene or toluene sulfonamide,naphthalene mono-, diand tri-sulfonic acids, o-benzoyl sulfimide, andone of its possible hydrolytic products, ortho sulfobenzoic acid.

Metasulfobenzoic acid is unique among aryl sulfon compounds from thestandpoint of introducing a minimum of sulfide sulfur into the nickelplate even at concentrations of 1 gram/liter and higher, and yet thiscompound is capable of markedly reducing the internal tensile stress ofnickel deposits especially those obtained from Watts type and sulfamatetype of acidic nickel electroplating baths.

While it is true that by using very low concentrations, such as 0.05 to0.1 gram/liter, of the usual aryl sulfon compounds such as benzenesulfonic acid, o-benzoyl sulfimide, and the other aryl sulfon compoundsmentioned above, it is possible to reduce the tensile stress of nickeldeposits, and not obtain much greater than about 0.01% sulfur in theplate, nevertheless, a slight excess of these aryl sulfon compounds willstart a very perceptible increase in the sulfur content of th nickelplate, and thus the control and maintenance of a consistent very lowsulfur content of the nickel deposit is quite difiicult and not of thehighest reliability.

When the meta sulfobenzoic acid is introduced into an acidi nickelsolution such as the Watts bath, there is no appreciable effect on theappearance of the deposit which remains dull gray. There is, however, avery definite beneficial effect on the reduction of the tensile stress.On the other hand, the widely used aryl sulfon compounds while reducingthe internal tensile stress of th nickel deposits also contribute veryappreciable amounts of sulfide sulfur (over 0.01%) to the nickel plateat the same time they confer luster and grain refinement.

It was found that if the meta sulfobenzoic acid is added to semi-brightsulfur-free nickel baths, such as Watts baths containing smallconcentrations of chloral hydrate or formaldehyde, the plate stays semibright and there is very little increase in sulfur content of the nickelplate, yet the tensile stress is very markedly reduced. Also the use ofmetal sulfobenzoic acid conjunctively with such compounds as theafore-mentioned aldehydes permits the operation of commercialsemi-bright electroplating solutions with wide tolerance to variationsof solution temperature and composition. For instance, a Watts typenickel solution which contains 3 grams/liter of the meta sulfobenzoicacid and 150 mg./l. of chloral hydrate may be operated at 150 F. whileproducing highly ductile semi-bright nickel deposits. In the absence ofthe sulfobenzoic acid, a gray, grainy deposit is obtained with poorductility of the nickel deposit at this temperature. This is achievedwithout introducing more than about 0.005 sulfur. Without themetasulfobenzoic acid present, the temperature of the bath must bereduced to around F. in order to obtain ductile plate.

The use of nickel deposits with a minimum of sulfide sulfur is importantin decorative protective applications of nickel-chromium deposits. Forinstance, the use of two layers of nickel, the first one substantiallysulfur-free and constituting at least 50% of the total nickel deposit,and the second containing appreciable amounts of sulfur, followed bychromium plate markedly increases the corrosion resistance of thecomposite compared to a single layer of bright nickel of equal or doublethe total thickness overlaid with the same chromium deposit. The firstnickel coating of such a double or duplex nickel system must besulfur-free or substantially lower in sulfur content compared to thesubsequent bright nickel which is plated upon it.

Nickel electrodeposits or electroforms used in engineering applicationsare often of greater thicknesses than thos used in decorativeapplications. These deposits must have excellent physical propertiessuch as high ductility and low tensile stress. In some engineeringapplications, it is desirable that the deposits be of a very high degreeof purity, and especially that the sulfide sulfur content is low.

The metal sulfobenzoic acid in a nickel sulfamate plating solution, forinstance, changes the stress from a tensile to a slight compressivestress. Under the plating conditions necessary to do this, the sulfurcontent of the deposit was only 0.003%.

Meta sulfobenzoic acid is effective with either fast agitation such asair, or with slower mechanical agitation of the cathode. The optimumconcentration ranges from 0.1 to 10 grams/liter. This compound can beused most effectively in nickel solutions such as Watts nickel baths,fluoborate and sulfamate baths and mixtures of these various acidicbaths. Boric acid is the preferred buffer, though acetic, succinic, orcitric acids can be used, though they are best used in conjunction withboric acid.

The best pH range is from about 2.8 to about 4.5. The temperature of thesolution may be from. room to about 180 F. although it is generallypreferred to maintain it from 120 F. to F.

When no air agitation is used, it is preferable to us a suitable wettingagent such as sodium octyl or lauryl sulfate or octyl sulfonic acid toprevent gas pitting. With air agitation, it is usually not necessary touse a wetting agent, but one which does not cause over-foaming, such assodium-2 ethylhexyl sulfate may be used.

The metasulfobenzoic acid not only cooperates with low concentrations offormaldehyde, chloral hydrate and bromal in making possible semi-brightnickel of improved ductility and minimum tensile stress when the bathtemperatures are raised :above the usual optimum temperatures, it alsocooperates, though not as strikingly, with the following unsaturatedcompounds: dimethyl fumarate, trimethyl aconitate, coumarin, 3-chlorocoumarin, 1,4 di(fl-hydroxyethoxy)butyne 2. In all these casessemi-bright nickel plate of excellent ductility and of very lowstressand very low sulfur content is obtained from Watts, sulfamate,kuoborate, bromide, and low all chloride (100 grams :per liter NiCl .6HO) baths. Also, improvements are obtained if the unsaturated compoundsare sufonic acids of the type of HOCH -CEC-CH OC H SO H, or the reactionproduct of sodium sulfite with r BIC H OC H OCH CECCH OC H OC H Br (ortheir chloro instead of the bromo derivatives) as detailed in UnitedStates Patent 2,841,602, issued July 1, 1958, under Method 4, col. 3.There is always the possibility that the sulfite group adds to thetriple bond and leaves a vinyl sulfonic type derivative (a sulfonicgroup attached to the unsaturated bond) whichal-so functions veryeffectively.

The metasulfobenzoic acid, by way of illustration, may be used in thebath formulations shown below to give lustrous, ductile, very lowstressed semi-bright nickel deposits which contain less than 0.01%sulfur. It is preferred to use the compound as the free acid or thenickel salt.

Example I Concentration, grams/liter NiSO .6H O 200-300 NiCl .6H O 15-50H BO 30-50 Meta sulfobenzoic acid 0.2- Chloral hydrate 0.03-0.2Formaldehyde 0.01-0.1

Example II NiSO .6H O 200-300 NiCl .6H O -50 H BO 30-50 Metasulfobenzoic acid 0.5-5 Chloral hydrate 0.04-0.21,4-di(fl-hydroxyethoxy)butyne-Z 0.01-0.1

Example III Ni(SO NH (nickel sul-famate) 250-500 NiCl .6H O 0-30 H BO30-50 Meta sulfobenzoic acid 0.5-5

Example IV NiSO .6H O 200-300 NiCl .6H O 30-60 H BO 30-50 Metasulfobenzoic acid 0.5-5

Coumarin and/ or 3-chlorocoumarin and/or dimethyl fumarate 0.050.4

I Example V NiSO .6H- O or Ni(SO NH 250-400 NiCl .6H O 0-30 H BO 30-50Succinic acid 0 5 Meta sulfobenzoic acid 0.3-7 Form-aldehyde 0.01-0.15Chloral hydrate 0.02-0.25

(nickel or sodium salt) 0.01-0.15

Example VI Ni(SO NH (nickel sulfamate) 250-500 NiBr 0-30 added to thebaths as a nickel salt.

H BO 3040 Meta sulfobenzoic acid 0.5-5

In the above cited siX examples, the preferred pH range is 2.8-4.5 andbath temperature 140-150 F. The cathode current densities may be anaverage of 40 to 60 amps/sq. ft. with air agitation, and much higherwith fast mechanical solution agitation.

The metasulfobenzoic acid is generally prepared by the sulfon-ation ofbenzoyl chloride or benzoic acid with chlorosulfonic acid. Themetasulfobenzoic acid is usually neutralized with nickel hydroxide ornickel carbonate, and It, however, can be added as the free acid, or assodium or magnesium, etc., salt. If too high a concentration of the freeacid is added to the nickel bath at one time the pH of the bath may dropbelow pH=1 and therefore the nickel salt of the acid is the preferredform for additions if concentrations greater than about 1 gram/liter areadded at one time. Of course, one would not use a copper or lead salt asthis would introduce well-known harmful metal ions. In general,therefore, the nickel salt or free acid is preferred. It should beunderstood that when metasulfobenzoic acid is referred to herein, theexpression includes the nickel salt of the compound. When the free acidis added to the nickel bath then due to the preponderance of nickel ionsover hydrogen ions, the metasulfobenzoic acid is mostly in the form ofthe nickel salt or ionized nickel salt. Small percentages of ortho andpara sulfobenzoic acid may be present in the metasulfobenzoic acid,though in general the more pure grades are preferred.

Besides the beneficial co-action of the metasulfobenzoic acid withformaldehyde, chloral hydrate and the aforementioned unsaturatedcompounds, it also cooperates to give ductile semi-bright nickel platewith other unsaturated compounds such as allyl alcohol and butyne diol,though in these latter cases, the cooperation is not quite as good aswith the previously mentioned unsaturated compounds.

What is claimed is:

1. A bath for the electrodeposition of ductile low-stress nickel platefrom an aqueous acidic nickel plating bath containing at least onenickel salt selected from the group consisting of nickel sulfate, nickelsulfamate, nickel fiuoborate, nickel bromide, and nickel chloride up toabout grams/liter of NiCl .6H O and containing dissolved therein about0.1 to about 10 grams/liter of metasulfobenzoic acid.

2. A bath for the electrodeposition of ductile semibright nickel plateof low stress from an aqueous acidic nickel plating bath containing atleast one nickel salt selected from the group consisting of nickelsulfate, nickel sulfamate, nickel fluoborate, nickel bromide, and nickelchloride up to about 100 grams/liter of NiCl .6H O and containingdissolved therein about 0.1 to about 10 grams/ liter of metasulfobenzoicacid, and an unsaturated compound selected from the group consising ofll HCH CCI CHO, CBr CHO, CH =C-CH OC H SO H, HOC H OOH CECCH OC H OH,and HOCH -CECCH OC H SO H, in a concentration of about 0.01 to about0.25 grams/liter.

3. A bath as claimed in claim 2 and wherein said unsaturated compound isformaldehyde in a concentration of about 0.01 to about 0.15 grams/liter.

4. A bath as claimed in claim 2 and wherein said unsaturated compound ischloral hydrate in a concentration of about 0.02 to about 0.25grams/liter.

5. A method for the electrodeposition of ductile lowstress nickel platecomprising the step of electrodepositing semi-bright ductile nickel froman aqueous acidic nickel plating bath containing at least one nickelsalt selected from the group consisting of nickel sulfate. nickelsulfamate, nickel fiuoborate, nickel bromide, and nickel chloride up toabout 100 grams/liter of NiCl .6H O, and containing dissolved thereinabout 0.1 to about 10 grams/liter of metasulfobenzoic acid.

6. A method for the electrodeposition of ductile semibright nickel plateof low stress comprising the step of electrodepositing semi-brightductile nickel from an aqueous acidic nickel plating bath containing atleast one nickel salt selected from the :group consisting of nickelsulfate, nickel suldamate, nickel fluoborate, nickel bromide, and nickelchloride up to about 100 grams/liter of NiCl .6H O, and containingdissolved therein about 0.1 to about 10 grams/liter of metasulfobenzoicacid, and an unsaturated compound selected from the group consisting of6 CClgCHO, CBr OHO, CHFC-CH OC H SO H, HOC2H4OCH2'CECCH2OC2H40H, andHOCH2CEC-CH2OC3H6S03H, in a concentration of about 0.01 to about 0.25grams/ liter.

7. A method as claimed in claim 6 and wherein said unsaturated compoundis formaldehyde in a concentration of about 0.0 1 to about 0.15grams/liter.

8. A method as claimed in claim 6 and wherein said unsaturated compoundis chloral hydrate in a concentration of about 0.02 to about 0.25grams/liter.

References Cited by the Examiner UNITED STATES PATENTS 2,841,602 7/ 1958Brown et a1. 204-49 X 2,849,353 8/1958 Kardos 20449 3,152,975 10/1964Kardos ct a1. 204-49 JOHN H. MACK, Primary Examiner. G. KAPLAN,Assistant Examiner.

1. A BATH FOR THE ELECTRODEPOSITION OF DUCTILE LOW-STRESS NICKEL PLATEFROM AN AQUEOUS ACIDIC NICKEL PLATING BATH CONTAINING AT LEAST ONENICKEL SALT SELECTED FROM THE GROUP CONSISTING OF NICKEL SULFATE, NICKELSULFAMATE, NICKEL FLUOBORATE, NICKEL BROMIDE, AND NICKEL CHLORIDE UP TOABOUT 100 GRAMS/LITER OF NICL2.6H2O AND CONTAINING DISSOLVED THEREINABOUT 0.1 TO ABOUT 10 GRAMS/LITER OF METASULFOBENZOIC ACID.